Anti-ribosomal P antibodies are associated with elevated circulating IFNα and IL-10 levels in systemic lupus erythematosus patients

OBJECTIVE: The objective of this paper is to analyze the relationship of anti-protein ribosomal P (RibP) antibodies with circulating levels of IFNα, TNFα, IFNγ, IL-17 and IL-10 in SLE. Disease activity and other systemic lupus erythematosus (SLE) features were also analyzed. METHODS: Anti-RibP and other SLE-related antinuclear antibodies (ANA) were determined by fluoro-enzyme immunoassay in the sera of 107 SLE patients. Circulating cytokines were quantified by flow cytometry (IFNα, IL-10 and IL-17) or ELISA (TNFα and IFNγ). RESULTS: Anti-RibP-positive patients (14.9%) displayed significantly higher serum levels of IFNα (p = 0.023) and IL-10 (p = 0.016) than their negative counterparts. This cytokine upregulation was independent of the presence of other ANA even though, in our patient cohort, anti-dsDNA was found to be associated with anti-RibP (OR, CI 95%: 6.03, 1.32-27.93, p = 0.021) and to correlate with IL-10 levels (r = 0.204, p = 0.036). In fact, patients positive for anti-RibP but negative for anti-dsDNA exhibited the highest amounts of both IL-10 and IFN-α that were not related to disease activity since these patients showed lower SLEDAI than patients also positive for anti-dsDNA (p = 0.018). Anti-RibP positivity was also associated with early diagnosis, hypocomplementemia and leukopenia. CONCLUSIONS: Presence of anti-RibP was found to be related to increased serum IFNα and IL-10 levels independently of both antibody status and disease activity.